OBJECTIVES: The development of the central nervous system and structures associated with the major embryonic axis including somites and kidneys requires at least two inductive protein factors (Tiedemann, 1971 Symp. Soc. Exp. Biol. 26:223). The biochemical properties of one of these factors (mesodermal inductor, MF) are nearly identical to those of protein synthesis initiation factor three (IF-3)--the protein regulating the binding of mRNA to the Met-tRNA-40S ribosomal complex. The overall objective of this research is to test whether MF and IF-3 are different names for the same molecule. RESULTS TO DATE: To test this hypothesis, a number of assays were needed. During the first and second years of this grant, we accomplished the following: (1) built a cell-free protein synthesis assay using wheat embryo extracts, (2) developed an isolation procedure for extracting chick embryo mRNA with high translational activity, (3) produced a heparin-sepharose affinity column to remove wheat initiation factors, (4) partially characterized wheat initiation factors bound to the heparin column, (5) characterized the products made through translation of our chick mRNA, (6) replaced wheat initiation factors with 0.5M KCl chick microsomal wash, and (7) began the development of a general procedure for the iodination of translationally active mRNA. THIRD YEAR OBJECTIVES: The objectives of this next year's research are as follows: (1) to produce 125I-mRNA with high translational activity and a reasonably high specific activity, (2) to use this labeled mRNA to develop a specific binding assay that will allow the purification of IF-3, (3) to isolate and completely characterize IF-3 from wheat embryo extracts, and (4) to begin the isolation and purification of chick embryo IF-3 from microsomal extracts using wheat extracts stripped of IF-3.